Commius the Gaul

Commius was a noble of the BelgicAtrebates tribe, who became an
aide to Julius Caesar and served as his ambassador to the British
tribes during both of the latter's expeditions to Britain in 55 and 54
BC, and was instrumental, it is believed, in persuading the British
king Cassivellaunus to eventually come to terms.

However Commius was later to change his mind regarding the wisdom of
co-operating with the Romans and joined with other Gallic leaders in an
ultimately unsuccessful revolt against Rome. But the attempt to relieve
Vercingetorix during the Siege of Alesia in 53 was repulsed by
Julius Caesar.

Commius then attempted to come to terms with Caesar
via his legate Marcus Antonius, but decided that he could not trust either and fled the continent in 51 BC, vowing never to set eyes on a Roman again.
We have a contemporary description (from the Strategematon by Frontinus) of how he managed to effect his escape from Gaul;

Commius, the Atrebatian, when defeated by the deified Julius, fled from Gaul to Britain, and happened to reach the Channel at a time when the wind was fair, but the tide was out. Although the
vessels were stranded on the flats, he nevertheless ordered the sails to be spread. Caesar, who was following from a distance, seeing the sails swelling with the full breeze, and imagining Commius
to be escaping from his hands and to be proceeding on a prosperous voyage, abandoned the pursuit.

Once in Britain he established himself as king over a group of existing Atrebatean settlers, or at least a tribe that had links with the continental Atrebates which he ruled from his capital at Calleva.

He died in around 35 BC and was succeeded by succeeded by a son also named Commius.

One or other of these Commius' was responsible, in around 30 BC for the production of the very first British inscribed coins, that bore the name COMMIOS with a triple-tailed horse displayed on the reverse.